Weak Gravitational Lensing by Galaxies

Abstract

Galaxies are biased tracers of the matter density on cosmological scales. For future tests of galaxy models, we refine and assess a method to measure galaxy biasing as function of physical scale k with weak gravitational lensing. This method enables us to reconstruct the galaxy bias factor b(k) as well as the galaxy-matter correlation r(k) on spatial scales between 0.01 h Mpc −1 k 10 h Mpc −1 for redshift-binned lens galaxies below redshift z 0.6. In the refinement, we account for an intrinsic alignment of source ellipticities, and we correct for the magnification bias of the lens galaxies, relevant for the galaxy-galaxy lensing signal, to improve the accuracy of the reconstructed r(k). For simulated data, the reconstructions achieve an accuracy of 3 − 7% (68% confidence level) over the above k-range for a survey area and a typical depth of contemporary ground-based surveys. Realistically the accuracy is, however, probably reduced to about 10 − 15%, mainly by systematic uncertainties in the assumed intrinsic source alignment, the fiducial cosmology, and the redshift distributions of lens and source galaxies (in that order). Furthermore, our reconstruction technique employs physical templates for b(k) and r(k) that elucidate the impact of central galaxies and the halo-occupation statistics of satellite galaxies on the scale-dependence of galaxy bias, which we discuss in the paper. In a first demonstration, we apply this method to previous measurements in the Garching-Bonn-Deep Survey and give a physical interpretation of the lens population.

Observational probes of cosmic acceleration

“…The earliest astrophysically interesting upper limit was that of Tyson et al (1984), who used the images of 200,000 galaxies measured by the now-obsolete method of digitizing photographic plates to exclude extended isothermal halos with v c > 200 km s −1 around an apparent magnitude-limited sample of galaxies. Galaxy-galaxy lensing was observed at ∼ 4σ by Brainerd et al (1996), the first clear detection of cosmological weak lensing. Their analysis used a total of 3202 lens-source pairs in a field of area 0.025 deg 2 .…”

Joint measurement of lensing–galaxy correlations using SPT and DES SV data

“…Gravitational lensing of the cosmic microwave background (CMB), for instance, was first detected (Smith et al 2007) by cross-correlating noisy CMB lensing maps with a catalog of radio galaxies. Similarly, in the context of galaxy lensing, the cross-correlation of lensing induced shearing of background galaxies with the positions of foreground galaxies (known as galaxy-galaxy lensing) was detected (Brainerd et al 1996) before shearshear correlations (Bacon et al 2000;Kaiser et al 2000;Van Waerbeke et al 2000;Wittman et al 2000). Furthermore, lensing-tracer cross-correlation measurements are typically less sensitive to additive systematic errors since these will tend to average to zero in the cross-correlation (assuming the sources of systematic error are uncorrelated between the lensing measurements and the tracer measurements, often a reasonable approximation).…”

Weak lensing constraints on the dark matter haloes of early type galaxies

“…Brainerd, Blandford & Smail 1996;Hudson et al 1998;Hoekstra et al 2004). In particular, Hoekstra et al (2004) report the detection of finite truncation radii based on the imaging data from the Red-Sequence Cluster Survey.…”

“…Here, we focus on the statistical mass estimates of field and cluster early-type galaxies obtained using weak gravitational lensing. Galaxy-galaxy lensing, the preferential alignment of faint background galaxies around bright foreground galaxies, was originally proposed as a method to constrain the masses and spatial extents of field galaxies (Brainerd, Blandford & Smail 1996), but has since been very successfully extended and applied inside clusters (Natarajan & Kneib 1996;Natarajan et al 1998;2002a). Constraints from this technique are statistical and probe the mass profiles at large radii, typically r >> 0.1r v ir .…”